Implement the 005-set-initiative feature that adds initiative values to combatants with automatic descending sort and active turn preservation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/application/src/index.ts

@@ -3,3 +3,4 @@ export { advanceTurnUseCase } from "./advance-turn-use-case.js";
 export { editCombatantUseCase } from "./edit-combatant-use-case.js";
 export type { EncounterStore } from "./ports.js";
 export { removeCombatantUseCase } from "./remove-combatant-use-case.js";
+export { setInitiativeUseCase } from "./set-initiative-use-case.js";

packages/application/src/set-initiative-use-case.ts

@@ -0,0 +1,24 @@
+import {
+	type CombatantId,
+	type DomainError,
+	type DomainEvent,
+	isDomainError,
+	setInitiative,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+
+export function setInitiativeUseCase(
+	store: EncounterStore,
+	combatantId: CombatantId,
+	value: number | undefined,
+): DomainEvent[] | DomainError {
+	const encounter = store.get();
+	const result = setInitiative(encounter, combatantId, value);
+
+	if (isDomainError(result)) {
+		return result;
+	}
+
+	store.save(result.encounter);
+	return result.events;
+}